Sterically Regulated Tetradentate Pt(II) Complex for Deep-Blue OLEDs with High Color Purity and Low Efficiency
Jiaoying Lin1, Feng Zhan1, Zhibin Li1
1Center for Phosphorescent Material Research, State Key Laboratory of Green Chemical Synthesis and Conversion, College of Chemical Engineering, Zhejiang University of Technology, Hangzhou, Zhejiang310014, P. R. China.
Abstract:
The realization of deep-blue phosphorescent organic light-emitting diodes (OLEDs) combining high color purity with low efficiency roll-off has proven to be a persistent challenge. Herein, we report a novel tetradentate Pt(II) complex, PtJYCz, based on a synergistic steric engineering strategy. A bulky 3,6-di-tert-butylcarbazole (DTBCz) group was appended to the carbazole moiety to suppress conjugation extension and narrow the emission spectrum, while a 3,3″,5,5',5″-penta-tert-butyl-1,1':3',1″-terphenyl(PTBTP) group was incorporated into the carbene unit to sterically shield the Pt(II) center and suppress intermolecular interactions. As a result, PtJYCz exhibited an ultranarrow deep-blue emission spectrum in solution with a full width at half-maximum (FWHM) of only 15.4 nm and achieved a high photoluminescence quantum yield (ΦPL) of 99% in poly(methyl methacrylate) (PMMA) films. The PtJYCz-based OLED displayed deep-blue electroluminescence peaking at 457 nm with Commission Internationale de l'Éclairage (CIE) coordinates of (0.135, 0.111), delivering a maximum external quantum efficiency (EQE) of 21.7% with suppressed efficiency roll-off, maintaining EQEs of 19.2% and 17.2% at luminance levels of 5000 and 10000 cd/m2, respectively. This work presents a rational molecular design strategy for narrowband deep-blue phosphorescent OLED materials.
